A widely-used circuit module includes a circuit substrate on which at least one mount component is mounted and a peripheral of the mount component is sealed with a sealing body made of a synthetic resin etc. When the mount component is a radiocommunication element, a surface of the sealing body is coated with a conductive material to be used as a shield against interruption induced by electromagnetic waves (hereinafter referred to as electromagnetic interruption). The electromagnetic interruption is interference, unnecessary radiation or the like, for example. By providing the shield, the electromagnetic interruption caused by the electromagnetic waves emitted from the mount component in the shield against electronic devices etc. outside of the shield is prevented (emission is improved), or the electromagnetic interruption caused by the electromagnetic waves emitted outside from the shield against the mount component in the shield is prevented (immunity is improved).
In addition, when a plurality of mount components are mounted on the circuit substrate, there is developed a circuit module where the shields are provided to separate the mount components in order to prevent the electromagnetic interruption between the mount components. As the mount components are covered with the sealing bodies as described above, the sealing bodies are partly removed to form trenches (grooves) and the trenches are filled with a conductive material to provide the shields between the mount components. The conductive material can be a conductive resin paste.
For example, Japanese Patent Application Laid-open No. 2010-225620 describes a circuit module where slits are formed on a mold resin layer and filled with a conductive resin to form shields between electronic components.